Telephone-transmitter



(No Model.) 2 SheetsSheet 1.' D. DRAWBAUGH.

TELEPHONE TRANSMITTER.

No. 272,865. Patented Feb. 27, 1883.

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UNITE STATES PATENT @FFECE.

TELEPHONE-TRANSM ITTER.

SPECIFICATION formng part of Letters Patent No. 272,865, dated February27, 1883.

Application filed December 5, 1882. (No model.)

To all whom it may concern Be it known that l, DANIEL DRAWBAUGH, ofEberlys Mill, Cumberland county, Pennsylvania, have invented a new anduseful 1mprovementiu Telephone-Transmitters,ofwhich the following is aspecification.

The invention relates to that class of telephones in which the currentis modified by changes in resistance of electrodes of carbon or otherlow conducting material placed in contact and acted upon by thevibrations of a diaphragm or sound-receiving mediutn.

The invention consists, first, in a novel arrangement of the carbons orlow conductors; and, second, in a new means ofadjusting the instrumentto renderit more or less sensitive, whereby it may be employed totransmit a noise produced before it for signaling purposes, so that thesame shall be loudly repro duced by the receiving-telephone, and wherebyit. may immediately be adapted for transmitting articulate speech.

It is a well-known fact that when a microphone is placed in verydelicate adjustment the sound transmitted by it will be reproduced by areceiving-telephone with great increase of volume and loudness,especially if the placrs of contact of the electrodes be reduced to merepoints or lines. It is also well known that when the instrument is thusarranged it is not possible practically to transmit articulate speech hyit, for the reason that it is exceedingly difficult to keep theelectrodes uniformly in such delicate contact. Hence they separate orbreak, and this results in theproduction of sharp, almost explosivesounds in the reeeivirig-instrument. This property of the microphone, Iam aware, has been utilized on telephonic lines to cause an ordinarymagnetoreceiving-instrutnent to emit a loud grating or buzzing sound toattract attention. In my present invention I avail myself of this sameproperty; but, instead of rendering it necessary to have in atransmitting-station one microphone or telephone-transmitter adapted fortransmitting speech by the undulatory current, and another microphonewith the electrodes' in very delicate contact, so as to transmit alarms,I provide a. single instrument, which may be adapted toeither purposeeasily and quickly without opening the inclosingcase or moving orinclining the instrument.

In the accompanying drawings, Figure 1 is a front view of theinstrument, with the outercover and diaphragm removed to show theinternal mechanism. Figs. 2 and 3 are vertical sections on the line 90 mof Fig. 1, showing the difi'erent positions assumed by the movable'carbons in accordance with the two adjustments of the apparatus. Fig. 4:is a horizontal sectionot the instrument on the line y y of Fig. 1,viewed from below. Fig. 5 is a plan view from above of the bottomcarbon. Fig. 6 is a rear view of the diaphragm. Fig.

-7 is a front view of an arrangement of the carbons which I adopt whenthe lower carbon is not made movable and adjustable. Fig. 8 is a sideview, showing the method of pivoting the intermediate carbons. Fig. 9shows separately the diaphragm when formed of a carbon plate; and Fig.10 is a partial sectional view, showing said diaphragm in place.

Similar letters of reference indicate like parts.

A is the back or base board of the instrument. B is the inclosing-case;O, the outer cover, having a mouth-piece orifice, D. The case,backboard, and cover I make preferably of wood.

E is the diaphragm, which may be of metal or a non-conducting material,such as a thin sheet of wood or rubber, or a low conducting material,such as carbon, as more particularly described hereinafter. e

G is a piece of'carbon cemented or otherwise suitably fastened to therear side of the diaphragm. When the diaphragm is of wood or othernon-conducting material I connect the carbon G, by means of a wire, a,to a small contact-piece of metahH, as shown in Fig. 6. When thediaphragm is of metal or of low-couducting material this wire andcontact-piece are unnecessary.

Resting on the lower side or bottom of the inclosing-case B, whichserves as a support, is a piece of carbon, I. (Shown separatelyin Fi 5.)In the underside of thiscarbon is formed a groove or channel, in whichprojects astnall pin, J. The pin J entersa slot, K, in the lever L. Saidlever, which is of metal or other suitable material, is pivoted at oneend to the side of the box at M. The free end of the lever L protrudesthrough a horizontal slot in the opposite side of the case, andterminates in a button or knob, N. The inner side of the box or casenext adjacent to the ends of the car bon I are lined with pieces ofmetal 0 O, with which the ends of the carbon are in contact. The carbon1 should be of such width as to fit neatly between said pieces of metal.The breadth of the carbon, as shown in Figs. 2 and 3, is approximatelyabout two-thirds the depth of the box or case, though I do not limitmyself to this exact proportion, as it may bewaried within reasonablelimits.

On the upper rear corner of the carbon I, I form a ridge, P, square intransverse section, except for a certain distance, Q, at about themiddle ot'its length, where it is rounded, as shown in section in Figs.2and 3. The square part of the ridge P thus forms shoulders at each endof the rounded part.

R R are two intermediate carbons, alike in shape, and formed as shown inFigs. 1, 2, and

3. The upper ends of these carbons are round-.

ed, so that the curved upper portion, when the carbons are in place,rests against the carbon plate G, which is secured to the diaphragm. Thelower extremities of said carbons R It are rounded and shouldered, asshown in Fig. 1, and provided with a groove or channel adapted toreceive the rounded part Q of the ridge P, as shown in Figs. 2 and 3.When the carbons R R are adjusted in place their outer lower sides meetthe shoulders formed by the square portion of the ridge P, and they arethus prevented from becoming laterally displaced at their lower ends.Between said carbons R R, I place a piece of paper or other insulatingmatcriahm, which may be cemented or otherwlse fastened to one of saidcarbons. The upper ends of the carbons R R are prevented from lateraldisplacemen t by the wooden bar S, attached to the back board, A, whichbar is recessed to receive thecarbons, as shown. Referring now moreparticularly to Figs. 2 and 3, it will be seen that when thelower carbonI is moved bodily forward by the lever .L engaging with the pin J thecarbons R R assume a more nearly vertical position,as represented inFig. 3, and that when said lower carbon I is moved backward by the samemeans the carbons R R are more inclined, as shown in Fig. 2.

It will be obvious that in the position of the parts shown in Fig. 3less of the weight of the carbons R R is borne by the carbon G than isthe case when the parts assume the position shown in Fig. 2; or, inother words, in the first case thecarbons RR press less heavily againstthe carbon Gr than they do in the second case. There is therefore a muchmore delicate or more easily-broken contact in the former circumstancesthan in the latter.

In practice I adjust the light contact as delicately. as possible. Theheavy contact should be so adjusted as that speech will betransmitsions.

ted easily without breaks. It is manifestly impossible to lay down anyexact angles of the carbons R R to the other low conducting blocks to beadopted for securing this result, inasmuch as the shape and size of theinstrument and relative proportions of the carbons may vary. Any one.-killed in the art of constructing modern carbon telephone transmitterscan, however, easily make adjustments once for all, which will beuniform, or very nearly so, in instruments made of the same dimen- Asthe forward and back movement of the free end of the lever L governs thelimit of adjustment-,it is easy to cut the slot through which the leverL passes in the side of the case to such a length as to restrict themovement of the lever as may be requisite.

Tis an induction-coil of the usual well-known construction, secured inany convenient way to the base-board A. The bar U serves to hold it inplace.

V is a spring-bar of metal, fastened at one endto the interior of thecase, and having its other end normally in contact with thepiece O.

W is an arm of the bar V, which projects through the side of the case;and X is a pin secured to the back board.

The circuits in the instrument proceed as follows: Starting from onepole ofthe battery, the current enters at the binding-post 1, and passesby the wire I) to the primary of the inductioncoil T, thence to themetal contact piece Y, thence to the contact-piece Hon the diaphragm,and by the Wire a to the carbon G, or, if the diaphragm is of metal,directly from contactpiece H to the diaphragm, and along the latter tocarbon G. From carbon G the'current passes to the carbons R R, thence tothe carbon 1, thence to the piece 0, thence to the spring-bar V, andthence by a wire, d, on the back of the base board A, and shown in Fig.l in dotted lines, to the binding-post 2, and thence to the other poleof the battery. The secondary circuit from the induction-coil proceedsby wires 6 e (dotted lines on back of case) to bindingposts 3 and 4, towhich are connected the terminals of the main or line wire. Connectedwith said binding posts 3 and 4 are branch wires ff, (dotted lines backof case,) which connect with the binding-posts 5 and 6,.to which posts areceiving-telephone may he attached.

The operation of theinstrumentis as follows: For signaling purposes theparts are adjusted as shown in Fig. 3-that is, with the carbons R R invery light contact with the carbon G. Sounds now made before thediaphragm cause the vibration of the latter, and result in either arapid series of makes and breaks of the circuit between the carbons R Rand carbon G or in a modification of the current so long as it remainscontinuous through carbons R R and G, whereby the sounds produced aregreatly augmented in loudness and volume in the receiving-instrument.Both, or either of these results may occur.

When it is desired to use the apparatus for transmitting speech theleverL is pushed back, thus sliding the carbon I to the rear, andcansing the carbons R R, as shown in Fig. 2, to lean at greater angleand more heavily against the carbon G. Theinstrument is then used as atelephonic transmitter of articulate speech in the ordinary way.

I do not limit myself to a low-conducting block. G, attached to adiaphragm of other material, conducting or non-conducting, as beforedescribed, as I have enlarged said carbonblock G, and made the same sulficiently thin to serve as a diaphragm, as shown in Figs. 9 and 10,securing it in the casein thesame way as is the diaphragm shown in Figs.2 and 3.

It is obvious that the wire a and contactpiece H will not then benecessary, inasmuch as the current will pass between the contactpiece Yand carbons R It directly over or through the diaphragm, as alreadydescribed in the case of a diaphragm of metal. This arrangement hasgiven good results; but 1 prefer the separate block of carbon attachedto a diaphragm of other material, as here shown, because the same ischeaper and more easily constructed.

The purpose of the peg X is to hang a receiving-instrument upon.

In the form of my device shown in Fig. 7 the lower carbon 1 is fastenedimmovably in the case, and consequently the adjusting-lever L and pin Jare omitted. This carbon is simply a thin bar of material without thegroove and ridge provided in the carbon I, but having a shallow channelor groove on its upper surface. The carbons RR, instead of beingsupported directly by the carbon 1, are

merely in contact with it at their lower ends, and are supported by abar of metal, F, fastened at one end to the back board, A, and then bentat right angles to serve as a pivot and pass through slots in thecarbons RR, as shown in Fig. 8. Washers h h are placed on the pivot F tokeep the carbons from lateral 5 displacement.

pieces of low conducting material placed in successive contact, andarranged between the (liaphragm or sound-receiving surface and asupport, the intermediate block being held in contact with the outerblocks by gravity, in combination with a means of moving one or more ofsaid blocks so as to alter the relative proportions of the weight of theintermediate block respectively supported by the outer blocks, and hencethe initial pressure between the adjacent blocks of the series,substantially as described.

2. In a telephone, three blocks, plates, or pieces of low conductingmaterial placed in successive contact, and arranged between thediaphragm or sound'receiving surface and a support, the intermediateblock being in contact with the outer blocks, in combination with ameans of moving one or more of said blocks so as to vary the anglesincluded be-.

tween the faces of the intermediate block and the adjacent surfaces ofthe outer blocks, substantially as described.

3. In a telephone, the combination of, first, a diaphragm; second, aplate, block, or piece of low conducting material attached to orvibrating with said diaphragm; third, an intermediate plate, block, orpiece of low conducting material of elongated form, substantially asshown, placed in an inclined position, with its upper end restingagainst the first-mentioned block or piece, and in contact therewith,and its lowerend in contact with,fourth, a piece or block of lowconducting material resting on a support not attached to or vibratingwith the diaphragm, substantially as described.

4. In atelephoue, the combination of the DANIEL DRAWBAUGH.

Witnesses FRED. M. OTT, M. W. JACOBS.

